Porsche Enthusiasts Club Forum

I thought I'd cracked it with a new relay, but no the HRW still refuses to work

The mirrors are heating up nicely, the lamp on the switch illuminates...but no power to the rear screen.

So I guess its the power feed through to the screen...probably a break in the wires? Before I start tearing the interior apart, can anyone advise of the routing of the HRW wires from the relay board to the rear hatch area.

Thanks

Jon

Original hatch struts or replacement? Theyre sided.

could just be the heating strips across the hatch glass are worn and have bits missing.They can easily get damaged if you load up boot and the hatch glass is rubbed on the inside .I think there is a good diagnosis method on Clarks Garage website.

Nick

Have a look at Clarks Garage website there is a good section on fault finding rear demister.You will need a voltmeter.

Nick

Deffo replacements. they aredifferent side to side, how do i check if theyare fitted correctly?

Thanks

Jon

Thanks Nick,

visual check on the grid looks good. I've checked the power feed to the wires entering the hatch area...and there is nothing coming through. I'm going to run power direct to the grid (with a proper fused input) and earthed to check the validity of the grid.

The mirrors heat up correctly so I know that the front end of the circuit and switch are allgood. it looks like I may have to rewire from the fusebox back to the rear hatch if everything else checks out.

regards

Jon

has it ever worked ? first establish if you have power to the wiring to the demister on the n/s connections on the strut and to the rear screen glass connection , then check across and see if the voltage decreases to 0 on o/s or to 0 somewhere in between on each heating element and report back.
Good luck.

Nick

Nick,

I don't believe it has never worked in the 7 years I've owned the car, however I cannot be certain a this year is th first time it's been used in damp conditions for many years...it normally lives in a heated garage! I had my suspicions but it's one of those jobs that I've only just got around to sorting out.

There is no power to the wiring to the demister checked in the hatch area (checked at the wire as it enters the hatch area....checked with the multimeter.

thanks

Jon

Hi, just in case you haven't seen this, here is the wiring diagram for the demister. If you haven't got any power at the hatch, I would just check the 25A fuse 4 and pin 30 of the relay for +12V first, could be there?



Hope that might help.

Without part numbers I dont really know. When the problem is caused by the struts its usual to get other electrical problems too. Sometimes just a fuse blowing but failed indicators are common.

Without part numbers I dont really know. When the problem is caused by the struts its usual to get other electrical problems too. Sometimes just a fuse blowing but failed indicators are common.

Thanks, that's a great help

Jon